The attorney-client privilege originated in Roman law, and flourished under what John Adams labeled "that most excellent monument of human art, the common of law of England." But in America, some states articulate their key privilege in statutes, some in rules, some in pure common law and some with a mixture of those.

In Becker v. Baptist Health Medical Group, Inc., the court pointed to "Article V of the Kentucky Rules of Evidence [which] includes no provision for common law development of testimonial privileges." No. 2022-CA-0074-MR, 2023 Ky. App. Unpub. LEXIS 410, at *12 (Ky. Ct. App. July 7, 2023). Not surprisingly, the court rejected a litigant's privilege claim – pointing to this rejection of any common law expansion. The court indicated that it would "strictly construe KRE 503 in accordance with 'the almost universally accepted rule that the testimonial privileges are generally disfavored and should be strictly construed.'" Id. at *15 (citation omitted).

Most states would not take such a narrow view – instead allowing the common law to provide nuance and some expansion of a statutory or rule-based attorney-client privilege standard.